This application is the national phase under 35 U.S.C. xc2xa7371 of PCT International Application No. PCT/KR01/02128 which has an International filing date of Dec. 7, 2001, which designated the United States of America.
(a) Field of the Invention
The present invention relates to a plasticizer composition, and particularly to a neopentylglycol ester plasticizer composition used for processing polyvinyl chloride resin and a process for preparing the same.
(b) Description of the Related Art
Polyvinyl chloride resin (PVC) is a common resin capable of realizing various physical processing properties by the appropriate mixing of various additives such as a plasticizer, a stabilizer, a filler, a pigment, etc. These various physical processing properties allow polyvinyl chloride resin to be extensively used as a material for various products such as pipe, electric wire, artificial leather, wallpaper, gloves, toys, etc. In addition, a plasticizer is an essential additive that, if added to polyvinyl chloride resin, gives a variety of physical properties and functions such as processability, flexibility, electric insulation property, etc.
Representative plasticizers used for processing polyvinyl chloride resin are phthalates, adipates, trimellitates, etc. One of the phthalates, di-2-ethylhexylphthalte (DEHP), is most commonly used, and it can also function as a standard plasticizer for evaluating performance of other plasticizers.
Neopentylglycol ester is used for enhancing miscibility of coolants or giving appropriate viscosity (U.S. Pat. No. 5,470,497), and it is used as an additive for brake fluid (Japanese Laid-open Patent Publication No. Sho 59-68248).
As mentioned above, neopentylglycol ester is mainly used for enhancing miscibility and optimizing viscosity, but it also has a plasticizer use. It has been recorded that a mono-ingredient ester, synthesized from neopentylglycol ester and an aliphatic compound such as butyric acid, 2-ethylhexanoic acid, etc. can be used as a plasticizer, but it is inferior to the existing plasticizers such as 2-ethylhexylphthalate in processing properties and it is not very compatible with polyvinyl chloride resin in plastisol processing.
The present invention is made in consideration of the problems of the prior art, and it is an object of the present invention to provide a multi-ingredient neopentylglycol ester plasticizer composition that is used as a plasticizer for preparing a processing product of polyvinyl chloride resin that has excellent tensile strength, elongation, static heat resistance, and viscosity stability.
In order to achieve these objects, the present invention provides a plasticizer composition comprising at least 3 kinds of neopentylglycol esters represented by the following Chemical Formula 1: 
(wherein R1 and R2 are independently a phenyl group or a C3-12 alkyl group, and preferably a C6-8 alkyl group).
In addition, the present invention provides a process for preparing the neopentylglycol ester plasticizer composition, and a polyvinyl chloride resin comprising the plasticizer composition.
The present invention will now be explained in more detail.
In plastisol processing, physical properties related to viscosity, namely initial sol viscosity and viscosity stability of sol, are important. Since plastisol processing products such as toys, taporin, etc. require different viscosity properties, plastisol processing requires appropriate viscosity control. The present invention provides a plasticizer for a polyvinyl chloride resin, and particularly a neopentylglycol ester mixture used for a plasticizer in plastisol processing.
The neopentylglycol (NPG) ester mixture includes a) 2-ethylhexanoic acid 3-(2-ethylhexanoyloxy)-2,2-dimethylpropyl ester, b) benzoic acid 3-(2-ethylhexanoyloxy)-2,2-dimethylol ester, and c) benzoic acid 3-benzoyloxy-2,2-dimethylpropyl ester. These three different kinds of esters can be represented by the neopentylglycol ester compound of the following Chemical Formula 1. 
(wherein R1 and R2 are independently a phenyl group or a C3-12 alkyl group, and preferably a C6-8 alkyl group).
The mixture preferably comprises 5 to 30 wt % of 2-ethylhexanoic acid 3-(2-ethylhexanoyloxy)-2,2-dimethylpropyl ester, 30 to 50 wt % of benzoic acid 3-(2-ethylhexanoyloxy)-2,2-dimethylpropyl ester, and 20 to 50 wt % of benzoic acid 3-benzoyloxy-2,2-dimethylpropyl ester.
The neopentylglycol ester plasticizer of the present invention, which allows excellent processing properties such as tensile strength, elongation, static heat resistance, and viscosity stability, when used for a plasticizer during processing of a polyvinyl chloride resin, is prepared by reacting benzoic acid and 2-ethylhexanoic acid with neopentylglycol.
The neopentylglycol ester mixture of the present invention, if added to polyvinyl chloride resin and processed, has tensile strength, elongation, static heat resistance, and viscosity stability that are superior to 2-ethylhexylphthalate, which is a standard plasticizer.
Mono-ingredient neopentylglycol esters, for example esters prepared by reacting neopentylglycol with C12 aliphatic acid, i.e., lauric acid, 2-ethylhexanoic acid, or benzoic acid, are difficult to use as a plasticizer in plastisol processing because they do not have compatibility with polyvinyl chloride.
Meanwhile, multi-ingredient neopentylglycol esters exhibit different physical properties according to the kinds and compositions of alcohol and monocarboxylic acid. For example, a multi-ingredient ester prepared by reacting isobutyric acid and benzoic acid with neopentylglycol has excellent operational efficiency because it has a low molecular weight, but it is inferior in static heat resistance and viscosity stability. On the other hand, a multi-ingredient ester prepared by reacting 2-ethylhexanoic acid and benzoic acid with neopentylglycol shows a great difference in tensile strength, elongation, and static heat resistance according to the compositions thereof, but little difference in viscosity stability.
As mentioned above, it is difficult for multi-ingredient esters as well as mono-ingredient esters to effect all physical properties such as compatibility with polyvinyl chloride, viscosity stability, static heat resistance, tensile strength, elongation, etc., and thus it is important to selectively synthesize acid and alcohol in an appropriate composition.
In addition, the viscosity stability of a plastisol is influenced by the structures of ester and polyvinyl chloride resin. An aliphatic acid ester is superior to an aromatic acid ester in viscosity stability.
Accordingly, in the present invention, a multi-ingredient neopentylglycol ester mixture with an appropriate composition is prepared from neopentylglycol and an appropriate acid and alcohol, i.e., the aliphatic acid 2-ethylhexanoic acid and the aromatic acid benzoic acid.
The neopentylglycol ester plasticizer is preferably prepared according to the following process.
In order to prepare a plasticizer composition comprising at least three kinds of neopentylglycol esters represented by the Chemical Formula 1, i) 10 to 30 wt % of neopentylglycol, ii) 20 to 50 wt % of 2-ethylhexanoic acid, iii) 20 to 60 wt % of benzoic acid, iv) 1 to 10 wt % of xylene, and v) 0.05 to 1 wt % of tetraisopropyltitanate are introduced into a flask equipped with an agitator and a condenser to react them at 200 to 300xc2x0 C. for 4 to 15 hours. Unreacted acids are removed by decompressing with a vacuum pump, neutralizing the reactant with 5 to 15 wt % of sodium hydroxide, and washing the neutralized reactant with water then decompressing and dehydrating it. An absorbent is added to the reactant and the reactant is filtered to obtain a final product, neopentylglycol ester plasticizer.
During the above process, the iv) xylene is an entrainer, and the v) tetraisopropyltitanate acts as a catalyst.
In addition, the present invention provides a polyvinyl chloride resin using the neopentylglycol ester composition as a plasticizer, which has excellent tensile strength, elongation, static heat resistance, viscosity stability, etc.
The present invention will now be explained in more detail with reference to the following Examples and Comparative Examples. However, these are to illustrate the present invention and the present invention is not limited to them.